The invention relates to a process for producing sanitary fittings or the like which are produced by plastics injection molding and have at least one seal. In addition, the invention relates to a sanitary fitting or the lake which is produced according to the process, is made of plastic and has externally and/or internally in each case at least one seal.
In the production of such sanitary fittings it has hitherto been necessary subsequently to assemble the separately produced parts--installed elements or basic elements, seals and the like--and then to carry out another leaktightness test, in particular also in the sealing region between the sealing element and the basic element holding it. This is comparatively complicated.
In the production of the basic element by means of all injection mold and two-part followers, care must be taken that the groove-like recess, for example for an external O-ring, in the follower-split region is produced as far as possible free of flash, since such flash call lead to leakages.
Leakages can also occur owing to a misalignment, appearing with time, of the two injection mold followers with respect to one another.
Care must also be taken that O-rings have, internally and externally, a surrounding parting line and that correctly positioned assembly is necessary for good sealing. If, due to rotation of the O-ring, the parting lines were to run round in a helical manner, leakage channels would form.
Because of the necessary prestressing of the assembled O-rings, an embrittlement of the sealing material is promoted, in particular in the case of relatively long mounting times.
If the fitting also has a seal, for example in the case of a non-return valve a lip seal interacting with a closure element, the assembly causes problems since this lip seal is very small and the handling during assembly is difficult. Since this seal is not secured and held after insertion, the position of the basic element during continued assembly must remain maintained such that the seal does not fall out again after insertion.
The seal must be secured in the insertion position by design measures in the other assembly parts, for example by means of a supporting ring to be fitted.
The individual assembly parts can only have very low dimensional tolerances, since otherwise the individual errors can accumulate until the total dimensional deviation is no longer acceptable. This relates to the annular groove or shaped groove for the sealing rings and also to the cross section of the seals themselves.
In the assembly of the individual parts, foreign bodies--hairs, fluff or other particles--can also come between the individual assembly parts, also leading to leakages.
The object of the present invention is to provide a production process and a product produced according to said production process in which the aforementioned disadvantages are avoided. The aim is in particular substantially to simplify the production and the assembly. Despite these simplifications, the aim is to achieve a particularly small dimensional tolerance of the finished parts, this being the case even for mass production involving large quantities. Finally, by means of the measures according to the invention, there should also be the possibility of design simplifications.
In order to achieve this object, it is proposed with reference to the process according to the invention that in a first operation, the basic element of the sanitary fitting is injection molded and, in at least one further operation, the material for the seal(s) is injection molded into the receiving openings present in the basic element for this.
By this process, the assembly steps for the attachment of the seals are dispensed with, since the latter are simultaneously injection molded in the injection molding machine. By means of this injection molding process, a good sealing in the transition region between the basic element and seal(s) is provided, so that, inter alia, leakage tests following the production or assembly are thereby no longer necessary as before. By means of the injection molding, the seals can also be held bonded to the basic element, so that no complicated additional measures in the assembly end the constructional design are necessary.
Any flash in the seating or mounting region of the seal(s) occurring during the production of the basic element, or other irregularities on the basic element, for example by a mold misalignment, no longer have a disadvantageous effect, since such irregularities are covered by the injection molded seals.
Special measures at the assembly station for keeping away foreign bodies--hairs, fluff--are now no longer necessary since the basic element and the seal(s) are present as a complete assembly unit at the assembly station.
Since the material of the seals injection molded on the basic element is in a relaxed position, a greater long-term stability and durability in the case of relatively long mounting can also be expected.
It is preferably provided that, in the case of assemblies having a plurality of seals, these seals are injection molded jointly in one operation, preferably via runners connected to one another.
Even in the case of a plurality of injection molded seals, the work outlay is thereby kept small.
However, there is also the possibility that in the case of assemblies having a plurality of seals, these seals are injection molded in succession, if required with different injection molding material.
This is advantageous particularly in the case of different injection molding material for the seals and also in the case of seals lying close to one another.
However, it is also possible to introduce different injection molding material for different seals in one injection molding operation if separate runners are provided and/or the distance between the seals is sufficiently great that a "mixing" of the different injection molding materials need not be feared.
The gating of the seals is expediently carried out outside the particular seal-seat region of the seals. Subsequent leakage points caused by gate marks are thereby avoided.
In the case of a sanitary fitting, in order to achieve the said object, it is proposed that the basic element of the fitting and the seal(s) be plastics injection moldings made of different material and that the seal(s) be closely bonded to the basic element by injecting molding on.
The basic element with the seal or seals is here virtually "cast in one piece", the close bonding of the seals consisting of a different, usually softer and more flexible material than the basic element, taking place during the injecting molding.
By means of the direct injection molding of the seal(s) onto the basic element, an especially good dimensional accuracy and dimensional constancy can be achieved, even in the case of large quantities of the assembly or the like.
If still further parts are to be bonded to the assembly, this can take place in more simple assembly steps in which, for example, a positional fixing of the seal(s) and the like is not necessary since these seals are already firmly bonded to the basic element. The assembly outlay is thus reduced.
The basic element expediently has, in the region of the seal(s), seating chambers in the form of open molded recesses, annular grooves or the like. Even when injection molded on, the seal can thereby have a cross-sectional volume necessary for elastic yielding and, moreover, is also held with a positive fit.
It is advantageous if, at the opening sides of the molded recesses or the like, gate points, if required additional gate points, are provided which are preferably located outside the seat-seal region, the seals having at least one, preferably surrounding cross-sectional recess from their outer seal-seat side in which the gate point(s) is (are) located.
Gate points directly at the "open" sides of the respective seal have the advantage that separate runners within the basic element are not required.
It is advantageous if, in the case of a plurality of seals arranged in particular adjacently, the molded recesses thereof in the basic elements are connected to one another via connecting channels which are filled with sealing material. A plurality of seals can thereby be injection molded from a common gating side and it is also advantageous that a retaining connection stabilizing the seals with respect to one another is provided by means of the connecting channels.
A preferred embodiment of the invention provides for the assembly to be a non-return valve with an external ring seal and with an internal lip seal interacting with a closure element and for the annular seal and/or the lip seal to be designed as plastics injection moldings and to be bonded to the basic element by the injection process.